The field of X-ray spectroscopy involves the measurement of the spectra of certain material being analyzed. Generally, the sample material being analyzed may be any liquid, slurry, powder material, or industrial gas that can occur in the run of industry. A sample is positioned in a cylindrical sample holder that includes a holder body forming a cell adapted to contain the sample. A disposable sample holder is generally made of plastic and is generally disposed of after a single use. A sample holder generally ranges in size between diameters of 20 to 57 mm and in height about 25 to 35 mm.
Sample holders include single open-ended cylindrical body type cells and double open-ended cylindrical body cells. For the double open-ended cell, a very thin plastic analytic film is placed as an X-ray transparent window across one of the circular end faces of the body of the holder, and the skirt of the film is then secured by a plastic securing ring to the outer wall of the body and the analytic film becomes taut. The body is then inverted so that the window face is positioned downwards. Alternatively, the plastic securing ring and the thin plastic analytic film is placed into a well of a sample holder film assembly device and one of the circular end faces of the holder body is placed over the film and the skirt of the film is then secured by the plastic ring to the outer wall of the body so that the analytic film becomes taut. The latter method is described in our Pat. No. 4,587,656. It is noted that the plastic securing rings are made of a thin, plastic, flexible material so that the thin analytic film can be gently yet firmly secured to the sample holder body. A double open-ended sample holder is illustrated in FIGS. 1 and 2 and discussed in relation therewith below.
In each of the above-described assembly methods, one circular end face is open so as to form a holder cell. The holder cell is then filled with the sample through the top open face of the cell. The sample may be a benign substance or it may be noxious, contaminated, caustic, or offensive. In addition, the sample may be treated with a solvent to dissolve the sample, the solvent itself being noxious.
After the sample material to be analyzed has been loaded into the sample cell and otherwise prepared for X-ray analysis, the cell is loaded into an X-ray sample cassette that is then moved into position for bombardment by X-rays. X-ray cassettes are cylindrical holders defining chambers into which the sample holder cell is loaded. Generally, the chambers of the cassettes have top edges that are of greater height than the height of the top edges of the sample holder cells. In addition, the diameters of the cassettes are generally only slightly greater than the diameters of the sample holders so that little space is provided between the wall of the cassette and the wall of the sample holder. Cassettes often have a spring-loaded screw-on cap over the cell.
In the present state of the art, a double open-ended sample holder is loaded into an X-ray cassette by hand by a technician. More in detail, the double open-ended cell is picked up by the technician, who may or may not be wearing protective gloves, transferred to a position above the cassette, and hand placed into the cassette. Also, the cassette may be located for loading purposes in an isolation chamber in which the double open-ended sample holder is placed into the cassette by a technician who manipulates the holder with flexible gloves that extend into the chamber.
In the process of X-ray analysis, when X-rays are directed at the bottom end of the cell body through the analytic film at the sample inside; the X-ray cause heat to be generated within the sample material. Many substances will not generate gases or vapors, or if they do so, such gases or vapors may be harmless to the X-ray equipment or the immediate environment. Certain sample substances, usually a liquid but at times a powder, upon heating will generate a vapor or a gas containing particles originating from the sample substance that should not be allowed to contaminate the X-ray machine or pass into the surrounding area. In such cases, the upper open face of the cell body must be covered to prevent passage of such contaminants. A problem exists, however, in that simple covering of the open face with a sheet of plastic film secured by a securing top ring or by a plastic cap will result in the sealing of the cell body so that a buildup of pressure within the cell body will occur upon generation of vapors therein. Such a pressure buildup will result in the bottom analytic film bulging outwardly from the cell along with the sample material thus distorting the entire process of the X-ray analysis.
In such cases where a top seal of the sample holder is required to prevent passage of vapor borne contaminants, a microporous film is secured across the top face of the cell body secured thereto by an upper securing ring. The microporous film will pass gases generated by the heated sample material but will filter out particles that would cause harm to the surrounding environment.
Microporous film is a gas permeable material, generally polypropylene or teflon, specifically intended to establish and maintain pressure equalization within a sample holder cell. Such film is characterized with the property of containing tortuous submicron-size passageways extending from one surface side to the other. This permits gases and vapors to permeate yet simultaneously prohibits the penetration of particles of the sample substance therethrough. Microporous film enables evacuation of entrapped gases through the micropores while at the same time relieves the sample holder of vapor pressure buildup. Under inert gas conditions such as helium, the micropores function as passageways for the gas to enter the sample holder cell and purge out any entrapped gases or vapors. In atmospheric operating conditions, the film helps maintain pressure equalization by continuously allowing the exchange of contained gases with the surrounding air environment. In all cases the immediate important consideration is to maintain a taut, thin-film sample support plane that defines the surface of the contained solution or powdered sample material. Any distension or convolution of the thin-film substance affects the sample-to-excitation source distance implying higher or lower than actual analytic concentration values.
In each of these cases the sample cell holder is in effect dropped into the cassette. This procedure is undesirable since the entire handling procedure for sample analysis requires gentle handling of the sample throughout the entire procedure of X-ray analysis, which includes gentle placement of the sample cell into the cassette.
Even greater problems occur with the removal of the sample holder cell from the X-ray cassette after the X-ray analysis. When the sample substances are noxious or offensive, spilling of the substances during removal of the cell from the cassette and during its transit to either a waste disposal station or to a recovery station often has undesirable results.
Remote handling caps for sample holders exist in the art, but not for microporous film covered holders. For example, our U.S. Pat. No. 4,575,869 describes a sample holder that includes a handling support for safe handling of the sample holder by either local or remote means. This handling support does not cover the case of a double open-ended cell where the top face of the cell must be covered by a microporous film. The top wall of remote handling caps also would be in proximity or in contact with the microporous film so that the integrity of the microporous film would be compromised.